The present invention relates to a color printer for printing a photograph, and more particularly, to a color printer for printing a photograph, which has a color filter with an improved structure.
FIG. 1 shows a schematic configuration of a general printer for printing a photograph. A holder 12 of a roll 2 of sensitized photographic paper is located in the upper left side of the body 1 of the printer as shown in FIG. 1. A tray 18 for receiving sheets of sensitized photographic paper is provided in the upper right side of the body 1 of the printer. The photographic paper 3 proceeds in the direction of an exposing portion 13 and a processing portion 16 which are provided between the roll holder 12 and the tray 18. A cutter 17 is located near the tray 18. The exposing portion 13 is positioned near an optical system (discussed below) and is constructed vertically so as to be able to expose the photographic paper as the paper proceeds downward vertically. The processing portion 16 which is used to develop and fix the exposed photographic paper, includes a plurality of feeding rollers and a processing chamber. A cavity 14 in which the exposed photographic paper resides temporarily is provided under the exposing portion 13.
The optical system comprises a light source 4 for generating light which exposes the photographic paper, a color filter 5 for transmitting specific colored light emitted from the light source 4, and a light diffusion box 6 for uniformly diffusing and advancing the light passing through the color filter 5. A negative film carrier 8 (hereinafter referred to as film carrier) and a table 7 for supporting the film carrier are located above the light diffusion box 6. An enlarging lens 9 for enlarging an optical image of the light passing through the film is provided above the table 7. A shutter 10 for controlling the passage of the light passed through the enlarging lens 9 is located above the enlarging lens 9. A mirror 11 for reflecting the light passing through the shutter 10 to the exposing portion 13 is installed above the shutter 10.
In a typical exposure, the light from the light source 4 becomes an image light by passing through the negative film of the film carrier 8. The image light passes through the enlarging lens 9 and reaches the photographic paper 3 via the mirror 11, forming an image on the photographic paper 3. In forming the image on the photographic paper 3, the formation time or exposing time depends on the opening time of the shutter 10.
FIG. 2 is a detailed view of the light diffusion box 6 and the color filter 50 of FIG. 1. Referring to FIG. 2, the light diffusion box 6 is located above a filter box 20. The light diffusion box 6 includes a housing with a mirror-processed interior, a diffusion plate 22 coupled to the top of the housing, and a glass plate 21 coupled to the bottom of the housing. Fine diamond formations are formed on the surface of glass plate 21. A film 25 supported by the film carrier 8 as shown in FIG. 1 is located above the light diffusion box 6.
Two sets (50 and 50') of color filters are provided inside the filter box 20. The upper color filter 50 is constructed to have a pair of opposing filter members 5b. This pair of filter members 5b is movably supported in the direction in which the two filter members are superposed on or detached from each other by an appropriate driving means and guiding means. The lower color filter 50' also has a pair of opposing filter members 5a. This pair of filter members 5a is movably supported in the direction in which the two filter members are superposed on or detached from each other, the same as members 5b of the upper color filter 50.
In the arrangement of the two sets of color filters 50 and 50', the upper color filter 50 may be a magenta filter with the lower color filter 50' being a yellow filter, or vice versa. This configuration may also include a cyan filter.
FIG. 3 is a plan view of a conventional color filter 50. Referring to FIG. 3, a pair of filter members 5 of the color filter 50 are basically rectangular. However, the central portion of the opposing ends (hereinafter referred to as the front ends) on the side which first overlaps when the filter members 5 move in the direction of superposition, is cut in the shape of a concave triangle. Each of the filter members 5 can move from a position in which they are opposingly spaced apart as indicated by phantom line 5A, to a position in which they are superposed on each other. In the latter position, the filter members 5 interpose a "light passing area" 30 through which light emitted by a light source 4 (refer to FIG. 1) passes.
When filter members 5 move in the direction of superposition, the front ends of the two filter members 5 first overlap the four corners of the light passing area 30. Thereafter, the front ends of the filter members 5 are superposed so that two triangular overlapping portions (c) (demarcated by both front end edges 51 of filter members 5 and the side edges of the filter members) are formed at both side edges of the light passing area 30. By doing so, a rhomboid filterless portion (b) is provided at the center of the light passing area 30. As filter members 5 continue to move in the direction of greater superposition, the overlapping portion (c) is increased gradually and the filterless portion (b) is decreased gradually. When the filter members 5 become overlapped to the utmost within a control section (a) of the color filter 50, the filterless portion (b) disappears.
In a photograph-printing color printer having such a conventional color filter 50, the filterless portion (b) (which remains until the filter members 5 overlap to the utmost) is located at the center (i.e., the point of highest luminance) of the light passing area 30. This results in a reduction in the color correction efficiency of the illumination light projected onto the film. To compensate for this, the light diffusion box 6 must be able to efficiently diffuse the illumination light transmitted via the color filter 50, otherwise color blotting will occur during printing. However, as shown in FIG. 3, the filter members 5 first enter the front portions of control section (a) via the respective corners of the light passing area 30, so that in order to efficiently diffuse light corrected by the filter members 5, the light diffusion box must be made sufficiently "long".
Therefore, in order to obtain a good-quality print (i.e., prints which are free from color blotting) using conventional filters, the light diffusion box 6 must be made sufficiently long, which impedes any attempt at miniaturizing the photograph-printing color printer.